Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
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Taxonomy and nomenclature<br />
Stipeae<br />
Nassella neesiana is a member <strong>of</strong> the Poaceae: Stipeae, “a cosmopolitan tribe ... widely distributed” with “major centres <strong>of</strong><br />
diversity in South and North America, <strong>Australia</strong> and Eurasia”, “primarily in temperate or warm-temperate regions” and<br />
“dominant in many <strong>of</strong> the arid <strong>grass</strong>lands <strong>of</strong> southern <strong>Australia</strong>, South America and Asia at varying elevations (0-5000 m)”<br />
(Arriaga and Jacobs 2006). The tribe contains “approximately 500” (Vásquez and Barkworth 2004 p. 484) or “c. 450” (Arriaga<br />
and Jacobs 2006) species. Simon (1993) erected a new subfamily Stipoideae for the tribe, a classification adopted by Watson and<br />
Dallwitz (2005), but not followed by others (e.g. Briese and Evans 1998).<br />
In the past Stipeae has been included with Poeae in a festucoid group, close to Miliceae, Diarrheneae and Nardeae (Tsvelev<br />
1984). The tribe was sometimes assigned to subfamily Arundinoideae (e.g. Barkworth and Everett 1986), and sometimes to<br />
Pooidae (Wapshere 1990) e.g. by Edgar et al. (1991), but molecular evidence indicated that it did “not sit comfortably in either<br />
subfamily” (Briese and Evans 1998 p. 94) and was not clearly delimited (Barkworth and Torres 2001). Zucol (1996) argued that<br />
phytolith leaf assemblages in Nassella species indicated an affinity with Arundinoideae, while Honaine et al. (2006) considered<br />
their phytolith study <strong>of</strong> Nassella and Piptochaetium spp. supported the assignment to Stipoideae. Molecular data currently<br />
indicates that Stipeae is monophyletic (Jacobs and Everett 1996) and it is now <strong>of</strong>ten considered a basal lineage within Pooidae<br />
(GPWG 2001, Arriaga and Jacobs 2006, USDA ARS 2006), or the largest <strong>of</strong> six tribes in Stipoideae, along with the monogeneric<br />
Nardeae, Lygeae, Ampelodesmae, Anisopogoneae and doubtfully Brachyelytreae (Watson and Dallwitz 2005).<br />
The tribe is best defined by characters <strong>of</strong> the embryo (Jacobs and Everett 1996) which are correlated with a set <strong>of</strong> characters not<br />
exclusive to the tribe: florets with a single spikelet, a coriaceous or firmer lemma with comparatively large unicellular<br />
macrohairs (Arriaga and Jacobs 2006), disarticulation <strong>of</strong> the seed above the glumes and absence <strong>of</strong> a rachilla extension (Jacobs<br />
and Everett 1996) (i.e. the rachilla is not prolonged (Jacobs et al. 1989)), a well-developed callus, and a terminal, usually<br />
articulated awn (Barkworth 1993). Stipoids are commonly wiry, “bamboo-like” perennial <strong>grass</strong>es (Jacobs et al. 1989 p. 570) and<br />
generally have a leafless, paniculate infloresence and a lemma that is tougher than the glumes (Barkworth and Everett 1986).<br />
For many years a large proportion <strong>of</strong> Stipeae were considered to be included in a broadly defined genus Stipa. From the late<br />
1970s taxonomic work led to the resurrection <strong>of</strong> old names and reassignment <strong>of</strong> species to other genera, some <strong>of</strong> very long<br />
standing (Barkworth and Everett 1986, Barkworth 1993, Jacobs et al. 2000, Barkworth and Torres 2001, Vásquez and Barkworth<br />
2004). The concept <strong>of</strong> Nassella (Trinius) E.Desvaux was expanded to include species with long florets, formerly in Stipa sens.<br />
lat. Barkworth (1990) recognised nine genera in Stipeae: Achnatherum, Anemanthele, Hesperostipa, Nassella, Oryzopsis,<br />
Piptatherum, Piptochaetium, Ptilagrostis and Stipa. Several additional genera are now recognised in the tribe: Jacobs and Everett<br />
(1996) assigned all <strong>Australia</strong>n native species formerly included in Stipa to the new genus Austrostipa and provided a key to the<br />
then ten genera <strong>of</strong> Stipeae; Peñailillo (1996) described a new genus Anatherostipa; Jacobs and Everett (1997) resurrected Jarava;<br />
Torres (1997) described Nicoraella; Vásquez and Barkworth (2004) defined a new genus Celtica for Stipa gigantea Link and<br />
resurrected the genus Macrochloa Kunth for Stipa tenacissima (Loefl. ex L.) Kunth. Barkworth (2006) included the small or<br />
monotypic genera Aciachne, Lorenzochloa, Macrochloa, Ortachne, Psammochloa and Trikeraia in her world list <strong>of</strong> Stipeae.<br />
Watson and Dallwitz (2005) included these 15 genera plus, tentatively, Danthoniastrum (possibly Aveneae). Tsvelev’s (1977)<br />
concept <strong>of</strong> Stipeae also included Orthoraphium Nees, Eriocoma Rydb., Streptachne R.Br., Stephanacne Keng and Pappagrostis<br />
Roshev.<br />
Barkworth (1990) <strong>review</strong>ed the complex taxonomic history <strong>of</strong> Nassella. The name was first used by Trinius 1830 at subgeneric<br />
rank. Barkworth (1990) expanded Nassella from c. 9 spp. to include 79 species, with most <strong>of</strong> the additions, including N.<br />
neesiana, being from Stipa sens. lat. Watson and Dallwitz (2005) probably relied on Barkworth (1990), giving a total <strong>of</strong> “about<br />
80” spp. for the genus. According to Barkworth and Torres (2001) Nassella included at least 116 spp., but Barkworth (2006)<br />
listed only 110. Quattrocchi (2006) gave an upper limit <strong>of</strong> 116.<br />
Barkworth (1990) considered Nassella to be most closely related to Piptochaetium and Hesperostipa. Analysis <strong>of</strong> morphological<br />
and anatomical characters placed Austrostipa close to Achnatherum and Ptilagrostis, but study <strong>of</strong> rDNA indicated a closer<br />
relationship to Nassella than to Achnatherum (Jacobs and Everett 1996). Detailed molecular and morphological examination<br />
(Jacobs et al. 2000) found Nassella and Piptochaetium to be sister groups; likewise for Austrostipa and Achnatherum.<br />
Austrostipa appears to be the most recently evolved genus in the tribe (Jacobs et al. 2000).<br />
Nassella is distinguished from other stipoid genera by having 3 stamens (1-3: Quattrocchi 2006); a tough lemma with three or<br />
more nerves and strongly and tightly overlapping margins, the outer margin extending 1/3 to 2/3 (25-50% Barkworth and Torres<br />
2001) <strong>of</strong> the way around the inner, an unridged surface, heavily silicified with round or oval silica bodies in the epidermis, the<br />
fundamental cells <strong>of</strong> the epidermis being extremely short and much shorter than wide, a solid apex <strong>of</strong>ten developed into a corona<br />
(crown) at the summit <strong>of</strong> the lemma, with cilia that <strong>of</strong>ten appear to be fused at the base; and a flat, veinless, usually glabrous,<br />
short, rudimentary palea, less than 30% as long as the lemma, and completely concealed by the lemma (Barkworth 1990,<br />
Barkworth 1993, Jacobs and Everett 1996, Barkworth and Torres 2001, Watson and Dallwitz 2005, Barkworth 2006; contra<br />
Stace 1997 p. 840: “palea 3x) as long as lemma”).<br />
Other common characters in the genus are the presence <strong>of</strong> both short and long anthers in a species or on the same plant or floret,<br />
tuberculate lemma, and abundant apical cilia on the long anthers (Barkworth 1990, Barkworth 2006). A many-noded culm with<br />
frequent branching is usual, but also occurs in Achnatherum and some Austrostipa spp. (Barkworth 1990). All Nassella species<br />
are caespitose perennials, the glumes are <strong>of</strong>ten strongly anthocyanic (anthocyanins = the water soluble glucoside compounds<br />
forming colouring matter in many flowers and other plant parts). No vegetative characters that distinguish the genus have been<br />
identified (Barkworth 2006). Nassella species are bisexual, mostly perennial, rarely annual, have hollow internodes and open<br />
sheaths and “readily deciduous” awns (Quattrocchi 2006 p. 1361).<br />
In the Americas Nassella species are found from southern South America to southern Canada at altitudes from 0-5,000 m. Two<br />
areas have particularly high diversity: the altiplano <strong>of</strong> the central Andes, and the pampas <strong>of</strong> Uruguay, southern Brazil and eastern<br />
Argentina (Barkworth and Torres 2001).<br />
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